Typical connectors used to connect an actuator rod to a valve stem often include a clamp assembly made from two pieces, each threaded at one end to connect to either the valve stem or the actuator rod. The two pieces are often fastened together by bolts, and provide a clamping force to keep the stem and rod from turning.
Current methods for manufacturing stem connectors are difficult, labor intensive, and costly, because they are made by machining carbon steel or stainless steel bar stock. Great care must be taken to manufacture these pieces because the threading must precisely match the threading of the respective actuator and valve stem to optimally secure the actuator to the valve stem. Because of these meticulous threading and tapping procedures, the two pieces that form a single stem connector assembly must always be kept in matched pairs so that assembly can be achieved, and damage to stem and actuator rod threads can be prevented.
However, matched pair stem connectors have many disadvantages. For example, because the threads of each pair must match up to one another, they are sent from the manufacturer as a unique set. Thus, the stocking, identification, handling, transportation, and assembling of these customized parts is expensive in that both pieces must remain together. The weight associated with two solid blocks forming the matched pair of stem connectors also creates extra labor, shipping, and other manufacturing costs.
Furthermore, in addition to manufacturing, assembling a stem connector for operative engagement with a valve assembly is typically an expensive, labor-intensive process. Illustratively, a general service valve assembly by-and-large features a bifurcated design. The bifurcated design requires careful arrangement of each half of the components comprising the valve assembly prior to locking the halves together. In particular, in one half of a valve assembly, the actuator and actuator rod, joins with the other half of the valve assembly, including the control valve and valve stem. Accordingly, each piece of the matched pair stem connector is integrated with a respective one half of the actuator rod and valve stem assemblies. Specifically, the threaded ends of the valve stem and actuator rod engage with the tapped holes of each piece of the matched pair stem connector. At least one fastening bolt, and often several, is also directed through the two pieces of the matched pair stem connector during the unification of the valve stem assembly. Thus, there are many difficulties associated with assembling the bifurcated valve stem connector in preparation for operation.
One design deficiency present in current stem connectors is the inability to accommodate a wide variety of actuator rod and/or valve stem lengths and diameter sizes. This is because a matched pair stem connector assembly is typically machined to accommodate only one specific size of valve and actuator stem. Also, so-called positioners, as mounted to an actuator assembly, actuator rod or stem connector, are often used to receive control signals from a processor, and thus, provide information for positioning the actuator rod with respect to the valve. However, many positioners cannot be coupled to a given stem connector. Unfortunately, due to size, space, and other constraints, and particularly if not built according to the known NAMUR or other standard specifications, stem connectors often do not accommodate a variety of stem positioner sizes and models. Thus, there is a long felt need for interchangeability of components associated with stem connectors.
Many of today's valve assemblies are expensive by design and feature numerous, heavy, and difficult-to-assemble components, but to remain competitive, often simple, low-cost components, including stem connectors, are required. Thus, valve stem connectors need to be inexpensive, reliable, easy-to-manufacture and easy to use, but many connectors do not satisfy these requirements.
Thus, there currently remains a need for a stem connector that is lightweight, compact, easy to machine, simple to operate and assemble, and is also interchangeable with other components associated with a valve assembly.